The availability of animal models has provided new insights into the pathogenesis of human disease. Recent external reviews of the SCOR have indicated a need for the availability of an induced animal model of arthritis to examine several key questions related to current projects. Collagen-induced arthritis (CIA) is one example of such an animal model that exhibits many of the features of rheumatoid arthritis (RA) in man. To address this issue and enhance its overall research activities, the SCOR proposes to add an Animal Model Core to the existing Monoclonal Antibody and Tissue Culture Core Facility. The specific aims of this core unit are two-fold: l) to make available to SCOR investigators the CIA model in mice and the resources for histopathologic analysis of mouse joint tissue and 2) to provide assays of mouse T cell function and cytokine production. These core unit activities will support project 2 by providing an animal model for investigating the significance of thrombin and the thrombin receptor in the pathogenesis of joint inflammation; and support projects 2 and 4 which are examining the possible role of nitric oxide (NO) in arthritis and its effects on inflammation and T cell function. Investigators in project 1 also will be supplied joint tissue to study various aspects of CD44 expression in synovium from mice with CIA. These core functions should broadly enhance ongoing work in the SCOR, stimulate new ideas worthy of further study, and build a valuable resource essential to many aspects of RA research.